The point data (Tapes 1 to 6) described by the metadata record 'Bathymetric surveys of Brown Bay, O'Brien Bay and Newcomb Bay in the Windmill Islands' were used as input data. This tab delimited data resulted from bathymetric surveys of Brown Bay by Jonny Stark (AAD) in February and March 1997 and includes latitude, longitude and depth fields. Latitude and longitude were obtained from differential ... GPS. The data were thinned to one point per 0.5m grid space using MATLAB. The boundary area for the O Brien Bay DEM was selected according to the distribution of data.
Soundings that were positioned above the current coastline data were deleted although the coastline data were not used as input data for the dem.
Vertices from the Australian Antarctic Data Centre's terrestrial contour data in the O'Brien Bay area (Dataset_id 11, Qinfo 17) were combined with the soundings. This combined point dataset was split and 90% used as a training dataset to create the DEM. The other 10% was used as a test dataset and used to validate the DEM.
The DEM (5m cell size) was created in ArcGIS 9.2 using the Geostatistical Analyst extension, with the input data in a UTM zone 49 projection.
In Geostatistical Analyst: The input data was split into a training and validation (test) dataset. the DEM was interpolated from the training dataset using a Kriging method; NODATA values were used in areas where there was no data the DEM was cross validated using the training dataset; and the DEM was validated using the test dataset.The dem was clipped using an analysis mask to eliminate large areas of no data.
Contours at 5m interval were generated from the DEM using the Spatial Analyst extension. Contours were smoothed and simplified using a tolerance of 2m. Contours greater than zero were exported to a terrestrial contour dataset called Contour_ln. Contours less than or equal to zero were exported to a bathymetric contour dataset called Bath_contour_ln.
The zip file available for download includes the training and test datasets as shapefiles, the DEM in ESRI's ArcInfo interchange and ASCII formats,files documenting the Kriging method and the validation results, and bathymetric contours derived from the DEM.
Usually mapped to a Universal Transverse Mercator projection, Zone 49S, Datum WGS-84.
The DEM is stored as an ESRI grid, a dem.asc - Arc/Info GridASCII format (Grid) and dem.e00 - Arc/Info export format (Grid).
The contour and bathymetry contour data is stored in esri shapefile format.